The Moon has a great influence on the Earth in part because of its large size in relationship to the Earth. The Earth exerts a strong gravitational pull on the Moon. The moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. Tides are caused by the pull of the moon's gravity on earth's surface. Land is too firm to respond noticeably to this pull, but water stretches toward and away from he Moon. On the earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite.
Astronomical Data
The distance from the Earth and Moon varies between 221,000 and 253,000 miles in a one month period due to the fact that the Moon moves around the Earth in an elliptical orbit.
The Moon orbits Earth showing a different phase, or lighting condition on its surface, at various times of the month. Each month the Moon goes from anew Moon, to a crescent, through to a full Moon, and then back again. Since the Moon orbits the Earth about once a month, these phases were used in ancient times as a basis for a lunar calendar.
When the Moon is on the opposite side of Earth from the Sun, the side we see is all lit. This is known as the "full Moon." When it is on the side of Earth that is near the Sun, the lit side is away from us and we don't see the Moon. In between those periods, the Moon is partially lit.
The Earth is moving in its orbit around the Sun in the same direction as the Moon and so the time needed to return to the same position is 29 days, 12 hours, 44 minutes, and 2.8 seconds. This is known as the synodic month and is the time interval that elapses between two successive full Moons. Because the rotation period of the Moon and the revolution period around the Earth are the same, the Moon shows the same hemisphere (called the near side) to Earth at all times. Conversely, one hemisphere is forever turned away from us (the far side.) Before the space age, the "far side" of the Moon was unknown. In October l959, The Soviet
LUNAR 3 spacecraft was the first to map the far side of the Moon showing craters, mountains, and lunar seas.